Mantivu North Western Puttalam
Lattitude and longitude: 7.911421°; 79.814406°
(modified by RB from Wikipedia)
Surface: 0.50 km2
They are two islands named "Mativu" in Sri Lanka; this one is located in the channel between Puttalam Lagoon and Mundal Lagoon, and the other one in Batticaloa lagoon.